Over a period of more than three decades, the Assignee of the present invention has demonstrated that its cut-off sawing systems using circular saw blades consistently out perform band saws and other cutting systems for cutting railroad rails, forging, billets and other workpieces made of metal. Specifically, equipment manufactured by the common Assignee of the present invention has utilized saw blades approaching six feet in diameter to cut workpieces of up to 24 inches in height and/or width at speeds 10 times faster than systems utilizing band saws. Use of the Assignee's circular cut-off saw systems has also repeatedly demonstrated an ability to cut more precisely, economically and reliably than other types of cut-off systems.
In order to achieve a high level of precision in cut-off length, and a smooth finish on the cut-off surface of the finished workpiece, using a circular saw blade, it is necessary to deal with a number of factors affecting the path of the saw blade as it enters and passes through the workpiece during the sawing operation. For example, the saw blade needs to be precisely constructed from suitable materials which will minimize dimensional inaccuracies of the blade itself, both at rest and while exposed to the working loads and heat generated during the cut-off process. The blade must also be accurately and securely mounted on a driving spindle in a manner which reduces wobble and run-out of the cutting edge. The configuration of the cutting teeth on the cutting edge of the saw blade can also influence on how true the blade will run and the nature of vibration introduced into the blade during the cutting operation. Such circular saw blades are also inherently distorted by vibration modes induced in the circular disk of the blade by the action of the teeth on the cutting edge impacting on and slicing through the workpiece.
Through the years, the Assignee and others involved in utilizing circular saw blades for cutting wood, metals and other materials have disclosed a variety of apparatuses and methods for dealing with the various factors influencing the performance of a circular saw blade. For example, commonly assigned U.S. Pat. No. 3,656,393 to Goellner discloses a method and apparatus for driving a saw blade and positively locking the saw blade to the nose of a driving spindle in a manner which minimizes backlash between the blade and spindle. Commonly assigned U.S. Pat. No. 4,463,645 to Goellner discloses a circular saw blade having a dual chip-cutting action in which all of the saw teeth are of like width and radial height to improve cutting action of the blade in a variety of respects, including significantly changing the manner in which the cutting teeth impact upon and cut through a workpiece in a way which positively influences deformation of the blade disk as a result of vibration induced by the cutting action of the saw teeth through the workpiece.
FIGS. 1-3 are schematic illustrations of a number of vibration modes for a center-clamped circular plate, such as a circular saw blade. Specifically, FIG. 1 is a chart tabulating a number of different vibration patterns which may be encountered in the center-clamped circular plate when excited at different natural frequencies. The solid straight lines and circles in the illustrations of FIG. 1 represent nodes, or areas where the displacement of the disk is essentially zero. The plus (+) and minus (−) markings on the illustrations in FIG. 1 show displacement of the disk out of or into the plane of the paper for the disk in each of the vibration modes illustrated in FIG. 1.
Those skilled in the art have long recognized that, for purposes of stabilizing a circular saw blade, it is the first mode of vibration as illustrated in FIG. 2 which is the most important mode to address. In the first mode of vibration, the disk A is essentially bisected by a single diametrically extending node B, with the hemispheres C, D of the disk A on either side of the node B cyclically deflecting in opposite directions from one another, as shown in FIG. 3, when the disk A is excited at the first natural frequency.
Through the years, a number of prior approaches have been disclosed for stabilizing a circular saw blade by placing matching pairs of stabilizers on opposite sides of the saw blade. The following US patent documents illustrate a number of prior approaches to stabilizing a circular saw blade, by placing pairs of stabilizer pads or other devices on opposite sides of the saw blade, with those pairs of pads being placed in some disclosures along a desired node line for the saw blade: U.S. Pat. No. 3,483,858 to Jansen; U.S. Pat. No. 4,136,590 to Kordyban; U.S. Pat. No. 4,563,928 to Salomonsson; U.S. Pat. No. 5,213,020 to Pleau; U.S. Pat. No. 7,127,978 to Boss; and US Published Patent Application 2006/0174497 to Belfiglio.
In general, these previous approaches to stabilizing a saw blade are directed toward circular saw blades used in rip-sawing arrangements. In rip-sawing, the conditions acting on the saw blade are different than for a typical cross-cutting arrangement. For example, in a rip-sawing arrangement, the workpiece along a longitudinal axis of the workpiece is typically mounted in some sort of movable carriage arrangement which directs the workpiece over, and pushes the workpiece past the saw blade, with the saw blade being mounted on a stationery cradle or frame arrangement. In cross-cutting arrangements, it is typically preferred to have the workpiece be mounted in a stationery cradle and have the saw blade mounted in a moveable carriage which can be manipulated to direct the saw blade across the longitudinal axis of the workpiece along an axis of motion in a cutting plane.
In a rip-sawing arrangement, providing stabilization for a saw blade is more readily accomplished, because the stabilizers can be mounted in a fixed location with respect to the circular saw blade. For cross-cutting saw operations, having the stabilizing elements in a fixed position with relation to the saw blade, at a location providing effective and efficient blade stabilization, has heretofore presented significant design difficulties, partly caused by having the blade move across the workpiece, as opposed to having the workpiece move across the blade.
What is needed, therefore, is an improved method and apparatus for stabilizing a circular saw blade, and particularly such an improved method and apparatus which is effective in a cross-cutting arrangement.